Various systems and processes for the production of liquid nitrogen have been known for many years, but the known systems have been more useful for the generation of large quantities of nitrogen used in large scale systems. For example, the Zimmerman U.S. Pat. No. 2,909,903 issued in 1959, shows a system designed to produce liquified gases at a rate of 110 liters per hour. A small research laboratory would generally require no more than 12 liters per hour. Unlike the Zimmerman system which uses two expansion engines and precooling, I have devised a miniaturized, portable, integrated system which can produce and store up to 12 liters of liquid nitrogen per hour using a small cryogenic refrigerator having a free piston displacer mounted in the neck of a Dewar container, and I generate nitrogen gas from ambient air pumped through a membrane separator. The entire system is capable of packaging in a compact portable unit.